In recent years, portable laptop computers have become popular. Frequently, such laptop computers are battery powered in order to enhance their portability. Preferably, a battery powered laptop computer can operate for an extended period of time under battery power before its battery must be either recharged or replaced. Also, the portability of laptop computers causes them to be transported, used, and stored in various environments, limited only by the imagination of their owners. Some of these environments may also reduce the operating lifetime of the battery or may even damage the laptop. Obviously, moisture can ruin a complex electronic circuit. However, moderate temperatures will reduce the operating life of a battery and may also permanently damage some integrated circuits within the laptop. These moderate temperatures may be tolerable to the user for brief periods of time but not to the laptop. Accordingly, it is important to reduce power consumption and to monitor the temperature of a sensitive integrated circuit in the electronic circuit.
Also, certain operating circumstances may require a data processor to be cooled by a heat sink, fan, etc. Heat sinks, fans, etc. are additional costs to the laptop and may limit the possible configurations of such systems. Generally, it is desirable to avoid the use of such cooling systems.
Previous power saving techniques disable power or disable clock signals to the electronic circuit in response to a specified event. Such a specified event may be a predetermined time elapsing without sensing a particular type of activity, may be the execution of specific software instruction, or may be the presence of a particular address on a bus. These techniques have various shortcomings. Some require knowledge beforehand that the electronic circuit can be powered down. Such knowledge is not often available. Others consume excess power while waiting for the initial idle time to elapse. Some require excessive time to restart a clock signal.
Previous temperature monitoring techniques have placed discrete circuits adjacent to the sensitive electronic circuit or have integrated simple sensors onto the integrated circuit itself. The sensitivity of the discrete solution is lessened by its large size relative to the size of a possible "hotspot" on the integrated circuit and by the thermal momentum of the sensor. The prior integrated solutions generate interrupts when the temperature of the sensor reaches some value. These solutions are not flexible enough to address the variety of issues raised by power and temperature management in current electronic designs.